How long should I rest between sets?

Sixty to ninety seconds for isolation work, two to three minutes for heavy compound lifts, and three to five for near-maximal sets. The heavier the set relative to your best, the longer the rest.

Does resting longer make the session worse?

For strength, no. Short rests cut the weight you can handle on the next set, which is the thing that drives the adaptation. Short rests only make sense when the goal is conditioning.

Why time the rest at all?

Because untimed rest drifts. Most people rest longer as a session goes on without noticing, and the last exercise ends up taking twice as long as the first.

Does it work with the screen off?

The timer holds the screen awake while it runs. It will not beep from a locked phone or a backgrounded tab.

Timer

Rest timer between sets

A single countdown for the rest between sets. Start it when you rack the bar, and it beeps when the next set is due.

The timer

Rest

The clock runs fullscreen and keeps the screen awake. It needs JavaScript, so with scripting off the plan below is the whole session written out.

Total: 1:30
Working: 1:30
Periods: 1

01WorkRest1:30

How it works

A rest timer counts one period down and beeps at the end of it. That is all a rest between sets needs, and it is the one thing a phone stopwatch makes annoying, because a stopwatch counts up and you have to keep looking at it.

Pick the rest length, press start when you finish the set, and put the phone down. The count runs large enough to read from a bench, and the last three seconds beep so you can be back under the bar on time.

Ninety seconds suits most accessory work. A heavy set of five on a squat wants three minutes, and the difference is not preference: at ninety seconds most people lose a rep or two on the following set purely to incomplete recovery.

Timing the rest is mostly a defense against drift. Rest is the part of a session nobody tracks, and it stretches quietly as the session goes on and the phone comes out. A session that should take fifty minutes takes seventy, and the last two exercises get rushed or dropped.

The number is worth revisiting rather than fixing forever. If the second set of an exercise is consistently much worse than the first, the rest is too short. If you are cold by the time the next set starts, it is too long.

Questions

How long should I rest between sets?: Sixty to ninety seconds for isolation work, two to three minutes for heavy compound lifts, and three to five for near-maximal sets. The heavier the set relative to your best, the longer the rest.
Does resting longer make the session worse?: For strength, no. Short rests cut the weight you can handle on the next set, which is the thing that drives the adaptation. Short rests only make sense when the goal is conditioning.
Why time the rest at all?: Because untimed rest drifts. Most people rest longer as a session goes on without noticing, and the last exercise ends up taking twice as long as the first.
Does it work with the screen off?: The timer holds the screen awake while it runs. It will not beep from a locked phone or a backgrounded tab.